1. Field of the Invention
The invention relates to insulators for induction machine conductors and in particular insulators for stub connectors that provide for electrical series inter-connection between stator coils in an induction motor.
2. Description of the Prior Art
Induction machines, such as medium and high voltage motors, have stators with arrays of multiple coil windings that are electrically coupled in series about the stator circumference. Typically stub-type connectors are utilized to form the inter-coil winding series connections when the coil windings are powered with approximately 6.6 kV or less voltage.
Stub connectors are externally insulated with multiple layers of insulative materials that are hand applied serially in layers. In any particular insulating application insulative materials utilized may include: double open-ended tubular sleeves constructed of fiberglass, acrylic, silicone; tape constructed of those materials, as well as mica and armor tape; and materials embedded or coated with resin accelerators or catalysts to instigate cross-linking and curing of insulative resins that are subsequently applied to the connectors during stator fabrication. As part of the insulation application process the layers are often tightly secured circumferentially about the stub connector with elastomeric or other stretch tape or double open-ended sleeves prior to application of resin, to assure that the insulation does not separate from the connector. Another commonly used way to secure insulation to stub connectors is with shrink tubing or tape that is secured by application of heat or other energy.
Application of insulation layers serially by hand is labor intensive and time consuming. Stub connectors are located in relatively confined locations about the stator axial ends that increase difficulties in applying individual insulation layers. Hand application also introduces potential variances attributable to different individual technicians, including their skill level, efficiency and physical capabilities.